Journal of clinical microbiology
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J. Clin. Microbiol. · May 2010
Rapid identification of bacteria from positive blood culture bottles by use of matrix-assisted laser desorption-ionization time of flight mass spectrometry fingerprinting.
Early and adequate antimicrobial therapy has been shown to improve the clinical outcome in bloodstream infections (BSI). To provide rapid pathogen identification for targeted treatment, we applied matrix-assisted laser desorption-ionization time of flight (MALDI-TOF) mass spectrometry fingerprinting to bacteria directly recovered from blood culture bottles. A total of 304 aerobic and anaerobic blood cultures, reported positive by a Bactec 9240 system, were subjected in parallel to differential centrifugation with subsequent mass spectrometry fingerprinting and reference identification using established microbiological methods. ⋯ The respective spectra showed low concordance to database references and were effectively rejected by score thresholds. Spiking experiments and examination of the respective study samples even suggested applicability of the method to mixed cultures. With turnaround times around 100 min, the approach allowed for reliable pathogen identification at the day of blood culture positivity, providing treatment-relevant information within the critical phase of septic illness.
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J. Clin. Microbiol. · Apr 2010
Matrix-assisted laser desorption ionization-time of flight mass spectrometry for direct bacterial identification from positive blood culture pellets.
An ammonium chloride erythrocyte-lysing procedure was used to prepare a bacterial pellet from positive blood cultures for direct matrix-assisted laser desorption-ionization time of flight (MALDI-TOF) mass spectrometry analysis. Identification was obtained for 78.7% of the pellets tested. Moreover, 99% of the MALDI-TOF identifications were congruent at the species level when considering valid scores. This fast and accurate method is promising.
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J. Clin. Microbiol. · Mar 2010
Comparative StudyComparison of polyurethane foam to nylon flocked swabs for collection of secretions from the anterior nares in performance of a rapid influenza virus antigen test in a pediatric emergency department.
Rapid antigen testing of upper respiratory secretions collected with various swab types is often utilized for laboratory diagnoses of influenza virus infection. There are limited data on the effects of swab composition on test performance. This study compared the performance of the Quidel QuickVue Influenza A+B test on secretions from the anterior nares when a polyurethane foam swab was used for collection to that when a nylon flocked swab was used for collection. ⋯ There were 56 cases of influenza detected by RT-PCR; the QuickVue test was positive for 40 foam and 30 flocked swabs, for sensitivities of 71% and 54%, respectively (P = 0.01). Similarly, there were 49 influenza cases detected by DFA and/or culture; the QuickVue test was positive for 38 foam and 30 flocked swabs, for sensitivities of 78% and 61%, respectively (P = 0.13). This study suggests that polyurethane foam swabs perform better than nylon flocked swabs for the collection of secretions from anterior nares in the Quidel QuickVue Influenza A+B test.
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J. Clin. Microbiol. · Mar 2010
Comparative StudyDirect ertapenem disk screening method for identification of KPC-producing Klebsiella pneumoniae and Escherichia coli in surveillance swab specimens.
Klebsiella pneumoniae carbapenemase (KPC) production in Gram-negative bacilli is an increasing problem worldwide. Rectal swab surveillance is recommended as a component of infection prevention programs, yet few screening methods are published. We compared detection of KPC-producing Klebsiella pneumoniae and Escherichia coli in surveillance specimens by 2 methods: (i) inoculation of swabs in tryptic soy broth containing 2 microg/ml imipenem followed by plating to MacConkey agar (MAC) (method 1) and (ii) streaking swabs on MAC onto which a 10-microg ertapenem disk was then placed (method 2). ⋯ The sensitivity and specificity of method 1 for detection of KPC-positive K. pneumoniae and E. coli in 149 rectal swab specimens were 65.6% (95% confidence interval [CI], 46.8% to 80.8%) and 49.6% (95% CI, 40.3% to 58.9%), respectively. With method 2, a zone diameter of < or = 27 mm had a sensitivity of 97.0% (95% CI, 82.5% to 99.8%) and specificity of 90.5% (95% CI, 83.3% to 94.9%) for detection of KPC in rectal swab specimens. Direct ertapenem disk testing is simpler, more sensitive, and more specific than selective broth enrichment with imipenem for detection of KPC-producing K. pneumoniae and E. coli in surveillance specimens.